Weather officials say extremely heavy rain is likely to continue in southwestern Japan's Kyushu region through Thursday. Some parts of the region are already facing a high risk of mudslides and flooding.
The officials may issue emergency warnings if downpours continue for several hours in the same areas. They are encouraging people in the region to evacuate without waiting for advisories to ensure their safety.
The meteorological agency says rain clouds are developing as a seasonal rain front hovers over the region and warm, humid air flows in.
Rainfall in some parts of southern Kyushu has reached 1,000 millimeters since Friday.
In some parts of Kagoshima and Miyazaki prefectures, it has amounted to between 400 to 600 millimeters in the last three days.
Weather officials have issued mudslide warnings in Kagoshima, Kumamoto and Miyazaki prefectures.
As of 9 p.m., risks of flooding were also increasing for low-lying areas near rivers in some parts of Kagoshima and Miyazaki Prefectures.
The officials say the rain front will become more active by Thursday, with localized downpours of more than 80 millimeters per hour for Kyushu.
There is also a chance of downpours in western Japan through Thursday night and in eastern Japan through noon.